DESCRIPTION (Applicant's Abstract): The long-term goal is to understand teratogenic mechanisms at the molecular level. Microphthalmia is a low level effect of methylmercury exposure and can be induced in early mouse embryos to reflect clinical disorders seen in exposed children. Gene expression arrays will be used to recognize fundamental biomolecular parameters that describe critical events leading to this malformation. Preliminary studies identified a critical response involving p53 tumor suppressor (Trp53) and peripheral-type benzodiazepine receptor (Bzrp), leading to the proposed focus on metabolic and regulatory pathways controlling mitochondrial DNA (mtDNA) genome expression. During neurulation, the embryo shifts from an anaerobic (glycolytic) to aerobic (oxidative) metabolism. This diauxic shift requires mtDNA genome expression and, consequently, a tight link between morphogenetic and metabolic differentiation. The investigators hypothesize control by retrograde regulation whereby a signal started in the mitochondrion leads to an adaptive response in the nucleus to culminate in mtDNA biogenesis. Four specific aims will begin to trace this pathway at the molecular level. Specific Aim 1, a teratological study, will determine exposure-disease relationships for methylmercury-induced microphthalmia with respect to dose response, genetic susceptibility (Trp53), and therapeutic intervention (Bzrp). Specific Aim 2 will use expression microarrays to profile gene expression for developing eye across the critical period of vulnerability (days 8-10 of gestation). Specific Aim 3 will profile exposure-disease pathways for methylmercury-induced microphthalmia with respect to dose-response, genetic susceptibility, and therapeutic intervention. Specific Aim 4 entails pathway integration to confirm cellular activities as they change over time. At ends we expect to build a searchable transcriptome database for the developing eye and a platform with which to discover the cellular pathways that hypothetically define a temporal sequence in dysmorphogenesis induced with methylmercury and other environmental toxicants.